Silicon pressure sensors offer multiple benefits that include small size, good quality, and stable performance. Further, since multiple identical sensors can be fabricated simultaneously on a single wafer, silicon pressure sensors are cost effective to manufacture. However, in certain environments, the pressure media can corrode components on the sensing die or the silicon sensing die itself. To prevent the pressure media from corroding the sensing die, the sensing die may be isolated from the pressure media. To isolate the pressure media, the sensing die is typically placed within an oil filled diaphragm system, where a metal isolating diaphragm is exposed to the pressure media on one side and to an oil filled chamber on the other. The pressure sensing portion of the silicon pressure sensor is surrounded by this oil, such that a change in the oil pressure results in a change on the sensing element of the silicon pressure sensor. However, an oil filled isolator system adds significant size to the pressure sensor structure compared to the size limit imposed by the silicon pressure sensing die.
Further, in certain implementations, where the pressure media is air, the silicon can be directly exposed to the air. In one type of pressure sensor, piezo-resistive silicon structures sense the strain in a pressure sensing diaphragm. The surface containing these piezo-resistive elements also contains metalized traces and wire bond pads. When air is the pressure media, the side of the silicon containing metalized areas for connecting the piezo-resistive elements can be exposed to air borne humidity. The humidity can result in current leakage between the metalized areas that produces errors in pressure measurements.